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2,5-Furandicarboxylic acid (FDCA) is an increasingly important platform chemical that may be produced via thermochemical, photochemical, electrochemical, or biocatalysis. Biocatalysis is preferred as it can be performed under mild reaction conditions, in an aqueous environment, and can involve benign oxidants (molecular oxygen) and biodegradable catalysts (enzymes and cells). Whole cells and isolated enzymes have both been demonstrated to effectively catalyze the biotransformation of HMF (5-(hydroxymethyl)furfural) to FDCA. Whole cell biocatalysts are robust and benefit from endogenously produced cofactors (which are otherwise expensive stoichiometric reagents). However, wild-type organisms suffer from catabolic pathways which yield many side products and catabolize FDCA. Thus, whole cells require metabolic modification to favor certain pathways and eliminate others to be viable. With clear pathways and simple reaction conditions, isolated enzymes allow for better control and easier product recovery. However, no individual enzyme effectively catalyzes the full oxidation of HMF to FDCA, and thus, cofactors, mediators, immobilization, mutation, or cooperation with other enzymes is employed to achieve complete oxidation. Herein, a comprehensive review of the biocatalytic methods for converting HMF to FDCA is presented. Moreover, general strategies for alcohol and aldehyde oxidation are also discussed to provide a more complete context.

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As epilepsy remains a refractory condition in about 30% of patients with complex partial seizures, electrical stimulation of the brain has recently shown potential for additive seizure control therapy. Previously, we applied noninvasive transcranial focal stimulation via novel tripolar concentric ring electrodes (TCREs) on the scalp of rats after inducing seizures with pentylenetetrazole (PTZ). We developed a close-loop system to detect seizures and automatically trigger the stimulation and evaluated its effect on the electrographic activity recorded by TCREs in rats. In our previous work the detectors of seizure onset were based on seizure-induced changes in signal power in the frequency range up to 100 Hz, while in this preliminary study we assess the feasibility of recording high frequency oscillations (HFOs) in the range up to 300 Hz noninvasively with scalp TCREs during PTZ-induced seizures. Grand average power spectral density estimate and generalized likelihood ratio tests were used to compare power of electrographic activity at different stages of seizure development in a group of rats (n= 8). The results suggest that TCREs have the ability to record HFOs from the scalp as well as that scalp-recorded HFOs can potentially be used as features for seizure onset detection.

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